U.S. patent number 4,308,516 [Application Number 06/122,871] was granted by the patent office on 1981-12-29 for plug-in fuse assembly.
This patent grant is currently assigned to Nissan Motor Company, Limited. Invention is credited to Susumu Hashimoto, Michio Kasamatsu, Syuichi Otani, Noriyasu Saito, Yukio Shimada, Teruo Suda.
United States Patent |
4,308,516 |
Shimada , et al. |
December 29, 1981 |
Plug-in fuse assembly
Abstract
A plug-in fuse assembly is disclosed which includes a fuse
element made up of a pair of elongated current-carrying portions in
spaced relationship and a fuse-forming link portion extending
between the current-carrying portions. The fuse element is placed
in an insulating casing with its terminal portions projecting
therefrom. Means is provided for providing a fuse opening
indication in response to heat generated from the fuse-forming link
portion when it opens up.
Inventors: |
Shimada; Yukio (Yokohama,
JP), Otani; Syuichi (Tokyo, JP), Hashimoto;
Susumu (Saitama, JP), Kasamatsu; Michio (Sakado,
JP), Suda; Teruo (Chiba, JP), Saito;
Noriyasu (Abiko, JP) |
Assignee: |
Nissan Motor Company, Limited
(Kanagawa, JP)
|
Family
ID: |
27282478 |
Appl.
No.: |
06/122,871 |
Filed: |
February 19, 1980 |
Foreign Application Priority Data
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Feb 19, 1979 [JP] |
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54-19063[U] |
Feb 19, 1979 [JP] |
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54-19064[U]JPX |
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Current U.S.
Class: |
337/241;
337/265 |
Current CPC
Class: |
H01H
85/30 (20130101) |
Current International
Class: |
H01H
85/00 (20060101); H01H 85/30 (20060101); H01H
085/30 () |
Field of
Search: |
;337/206,241,242,243,244,265,266,267 |
References Cited
[Referenced By]
U.S. Patent Documents
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2702329 |
February 1955 |
Dietz, Jr. et al. |
3924216 |
December 1975 |
Martin et al. |
4127837 |
November 1978 |
Borchart |
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Foreign Patent Documents
Primary Examiner: Harris; George
Attorney, Agent or Firm: Lowe, King, Price & Becker
Claims
What is claimed is:
1. A plug-in fuse assembly comprising:
(a) an insulating casing formed therein with a cavity;
(b) a fuse element placed in said cavity of said casing, said fuse
element made up of a pair of elongated current-carrying portions in
spaced relationship, and a fuse-forming link portion extending
between said current-carrying portions, said current-carrying
portions having their bottom end portions extending from the bottom
margin of said casing and their top end portions extending through
the top wall of said casing; and
(c) a resistance member placed on the outer surface of the top wall
of said casing in contact with the top ends of said
current-carrying portions to form a shunt electric circuit with
said fuse-forming link portion, said member having a high
resistance with its color changed when exposed to high temperature
caused by current flow through said resistance member when said
link portion is open.
2. A plug-in fuse assembly according to claim 1, wherein said
member is formed of a high-resistance metal plate having on its
surface a heat responsive coat.
3. A plug-in fuse assembly according to claim 1, wherein said
member is formed of a heat responsive semiconductor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in a plug-in fuse assembly
and, more particularly, to a plug-in fuse assembly which provides
an indication to the user when the fuse opens up.
2. Description of the Prior Art
Plug-in fuse assemblies have been widely accepted by virtue of
their great potential for compact and inexpensive designs. For
example, U.S. Pat. No. 3,909,767, to Williamson et al. issued Sept.
30, 1975 shows and describes in plug-in fuse assembly.
As illustrated in perspective form in FIG. 1, such a conventional
plug-in assembly comprises a fuse element 1 stamped from a strip of
fuse metal, and a synthetic plastic molded casing 2 with a space
therein in which the fuse element 1 is placed. The fuse element 1
is comprised of a pair of elongated current-carrying portions 3
projecting in spaced parallel relationship from the bottom margin
of the casing 2 and a fuse-forming link portion 4 extending between
the current-carrying portion 3 to interconnect them. The top ends 5
of the current carrying portions 3 are exposed so that test probes
can contact with the current carrying portions 3.
One of the difficulties with such a conventional plug-in fuse
assembly is that testing means and troublesome manipulations are
required in testing for the continuity of the fuse-forming link
portion.
SUMMARY OF THE INVENTION
In view of the foregoing, a general object of the present invention
is to provide an improved plug-in fuse assembly which permits the
user to check the continuity of the fuse with greater ease.
Another object of the present invention is to provide an improved
plug-in fuse assembly which can provide an indication when the fuse
opens up.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, as well as
other objects and features thereof, reference is had to the
following detailed description of the invention to be read in
connection with the accompanying drawings, wherein;
FIG. 1 is a transparent view showing a conventional plug-in fuse
assembly;
FIG. 2 is a longitudinal sectional view showing one embodiment of a
plug-in fuse assembly made in accordance with the present
invention;
FIG. 3 is a top plan view of the fuse assembly of FIG. 2;
FIG. 4 is a longitudinal sectional view of the fuse assembly of
FIG. 2 showing the condition of opening of the fuse-forming link
portion;
FIG. 5 is a longitudinal sectional view showing a second embodiment
of the present invention; and
FIG. 6 is a longitudinal sectional view showing a third embodiment
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIGS. 2 to 4, there is illustrated one embodiment
of a plug-in fuse assembly made in accordance with the present
invention. The plug-in fuse assembly comprises an insulating casing
12 formed therein with a cavity 14 opening at its bottom end and
having its top wall 16 provided with through-holes 18. The casing
12 may be a molded part made of an insulating material such for
example as vinyl chloride.
The plug-in fuse assembly also comprises a fuse element 20 which is
made up of a pair of elongated current-carrying portions 22 in
spaced parallel relationship and a fuse-forming link portion 24
extending between the current-carrying portions 18 to interconnect
them. The fuse-forming link portion 24 is preferably both narrower
in width and smaller in thickness than the current-carrying
portions 22 of the plug-in fuse element 20 so that it can open up
with heat generation if an excessive flow of electric current is
conducted therethrough. The plug-in fuse element 20 may be a single
stamping from a strip of fuse metal such for example as a zinc
alloy. The fuse element 20 is inserted into the cavity 14 of the
casing 12 through its bottom opening and placed therein with the
current-carrying portions 22 having their terminal portions 26
projecting outwardly from the bottom margin of the casing 12 and
having their top end portions 28 extending through the holes 18 of
the casing 12.
A high-resistance, heat-responsive member 30 is placed on the outer
surface of the top wall 28 of the casing 12 in electrical contact
with the top ends of the current-carrying portions 22. The
high-resistance, heat-responsive member 30 may be a high-resistance
metal plate having on its surface a heat responsive coat, a heat
responsive semiconductor film or layer, or the like having a high
resistance with its color changed when exposed to high temperature.
The high responsive material is preferably of the type having a
property to maintain the color changed after it is once
changed.
In view of minimization of the shunt current flow through the
member 30 when the fuse is closed and great circuit protection when
the fuse opens up, the resistance of the high-resistance,
heat-responsive member 30 is preferably selected at 50 or more
times the resistance of the fuse-forming link portion 24.
With the plug-in fuse assembly of this embodiment, if the
fuse-forming link portions 24 of the fuse elemment 20 is exposed to
an excessive flow of current, it will open up and the current flow
through the high-resistance, heat-responsive member 30 to heat it
and change the color thereof as shown in FIG. 4. This provides a
fuse opening indication to the user.
Referring to FIG. 5, there is illustrated a second embodiment of
the present invention wherein like parts are designated by like
reference numerals. In this embodiment, the insulating casing 12 is
formed of thermoplastic resin such for example as vinyl chloride
and has its top wall 16 thinned at least partially. The
fuse-forming link portion 24 of the fuse element 20 is positioned
near the top wall 16 of the casing 12.
With this arrangement, if there is an excessive flow of current
through the fuse-forming link portion 24, it will open up with
generating heat to deform or brake the thinned portion of the of
the top wall 16. This can be viewed by the user.
It is preferable to deposit, on the outer surface of the top wall
16 of the casing 12, a heat responsive film 32 which has its color
changed when exposed to high temperature. This provides a more
reliable fuse opening indication to the user. The heat responsive
film is preferably of the type having a property to maintain the
color changed after it is once changed. The deposition of the heat
responsive film may be accomplished by coating a heat responsive
material.
Referring to FIG. 6, there is illustrated a third embodiment of the
present invention wherein like parts are designated by like
reference numerals. In this embodiment, the casing 12 is formed of
an insulating material high in transparency and a heat responsive
film 34 is deposited, such as by coating, on at least a part of the
surface of the fuse-forming link portion 24 of the fuse element 20.
The heat responsive film 34 has its color changed when exposed to
high temperature and preferably has a property to maintain the
color changed after it is once changed.
With this arrangement, the fuse-forming link portion 24 opens up
with generating heat to change the color of the heat responsive
film 34 deposited thereon when exposed to an excessive flow of
current. This can be viewed by the user through the transparent
casing 12.
It is to be noted, of course, that the heat responsive film 34 may
be deposited on the whole surface of the fuse element 20.
In view of the foregoing, it is apparent that there has been
provided, in accordance with the present invention, an improved
plug-in fuse assembly which provide a fuse opening indication which
the user can note with ease. While this invention has been
described in conjunction with specfic embodiments thereof, it is
evident that many alternatives, modifications and variations will
be apparent to those skilled in the art. Accordingly, it is
intended to embrace all alternatives, modifications and variations
that fall within the spirit and broad scope of the appended
claims.
* * * * *